Bilateral implantation has yielded considerable improvements in cochlear implant (CI) performance. However, bilateral CIs are generally programmed clinically as two independent devices. As a result, the full potential of bilateral implants remains untapped. Multiple electrodes can activate overlapping neural populations and thus cause similar percepts ("perceptual overlap"). Perceptual overlap between ears is critical for perceiving binaural cues, particularly interaural time difference. Bilateral CIs can be optimized to maximize the perceptual overlap of electrodes that are matched-up across ears ("matching"), which is not currently done clinically. Perceptual overlap within each ear can considerably limits CI performance. Bilateral CIs can be optimized to reduce the perceptual overlap between electrodes by dividing the signal across the ears, sending adjacent frequency regions to opposite ears ("interleaving"). With matching, where the same frequency regions are sent to both ears, electrodes that are bilaterally matched need to yield the maximum perceptual overlap. With interleaving, where signals from different frequency regions are sent to opposite ears, such pairings need to be avoided. The benefits of matching versus interleaving may vary across patients, and some patients may receive optimal benefit from combining the two methods over different portions of the electrode array. Our long-term goal is to optimize bilateral stimulation for difficult listening situations. We hypothesize that optimally pairing electrodes across ears will improve the perception of spatial cues. We also hypothesize that minimizing the perceptual overlap within and across ears will provide additional spectral cues. Finally, we hypothesize that combining bilateral matching and interleaving for different cochlear regions will maximize the benefit of bilateral implantation.

Public Health Relevance

Bilateral cochlear implant users have difficulty with challenging listening tasks such as understanding speech in noisy environments. The proposed research aims to optimize bilateral electric stimulation. The proposed research is clinically significant because it will help optimize the clinical fitting of bilateral cochlear implant patiens and will benefit cochlear implant users by improving their communication abilities, especially in difficult listening environments.